Mechanical negative process and resist



United States Patent MECHANICAL NEGATIVE PROCESS AND RESIST Harold A.Molz, Arlington, Va., and James Edward Peake, Bladenshurg, Md.

No Drawing. Application June 21, 1952, Serial No. 294,934

8 Claims. (Cl. 41-46) This invention relates to processes of producingfilms adapted for use in the preparation of photolithographic plates andthe like. More specifically, the invention relates to processes ofpreparing either positives or negatives of such films directly from hottype without the aid of lenses, cameras, dark rooms or other specializedphotographic equipment. The films produced in accordance with theteachings of the present invention are comparable in use and quality toconventional films in use in the art of producing lithographic printingplates and are even superior in some respects.

The invention contemplates the production of lithographic negativesand/or positlvesdirectly from hot type, that is, type produced from alinotype machine, a monotype machine or hand-set machine-cast type, ortype hand-set from a case of type. The negative or positive is producedwithout the use of a camera and without the use of any equipment otherthan that normally used in the process of preparing and set-ting typeand pulling proofs on paper or acetate sheets, with the exceptionhowever that the present process uses ordinary commercial photographicfilm and more particularly those films now normally used in thelithographic art, which films are characterized in that they have a finegrain, relatively thin emulsion coating and an. extremely high contrast.In the processing of such films, commercially available developing andfixing baths and dissolving solutions are used. However, a specialresist may be employed under certain conditions as indicatedhereinafter.

In the conventional method of preparing films for use in the preparationof lithographic printing plates, it is customary to set up the type orother material to be copied end, after inking the type a page proof ismade. The

impression made on the page proof is. then photographed with acommercial type camera having lenses particularly adapted for the typeof work in question and as a result of the photographing of the materialon. the page proof a film negative is prepared in the usual mannor byemploying a dark room and the. successive chemical treatments ordinarilyused in developing conventional films. Care must be taken to see. thatthe film is not pre-exposed before it is placed in the camera and caremust also be taken to. see thatthe film is not exposed to light uponorafter being removed from the camera until the. developing process hasbeen completed under dark room eonditions..

An important aspect of the present invention is that any photosensitive,article. comprising a transparent or trans- ,lucentbase; being providedon one. surface thereof with a highrcontrast emulsion such as. thatknown in the trade as Eastman Kodalitlr Film or Duponts LithoTransparentpaperfilrn may be used as the photographic film. The light-sensitiveemulsion such as silver halide, on the surface of such-a film is printedfrom a blanket with a certain typeresist, ina manner such as referre'dto as dry offset to impress. thereon the image desired. in the ultimatephotolithographic plate. Thepresentfinvention contemplates that a resistcomprise a fluorescein of the Rhodamine type since such resist hasproved most successful in the present process. The film, after having animage printed thereon is, before or after impression, subjected toexposure to normal room light (or stronger) and is treated with certaindeveloping and fixing baths to produce a lithographic film capable ofuse directly in the lithographic printing art, that is, a lithographicprinting plate can be made directly from the film so produced.

An important object of the invention is to provide a particular class ofresists which will be stable and insoluble in the presence of either adeveloping solution or hypo solution, and yet be capable of beingremoved by nonaqueous solvents. Thus when the printed or impressed film,having been printed or impressed on its, emulsion side, is placed in oneof the well known developers, such as Eastman Kodalith Developer, theresist will stand up, that is, not react with or be dissolved by thedeveloper whereby the emulsion lying directly beneath such resist isprotected and preserved .until a later stage in the process. Uponfurther treatment of the resist with a non aqueous solvent such asvarsol, gasoline, turpentine, or the like, the resist will be dissolvedand removed from the surface of the film. Thereafter, the film is placedin a fixing bath such as sodium thiosulphate solution and afterwardswashed and dried to produce the desired negative.

if it is desired to produce a positive film, it may be done by reversingthe sequence of the developing and fixing steps. Thus, when the printedor impressed film, having been printed or impressed on its emulsionside, is placed first in a fixing bath such as sodium thiosulphatcsolution, the resist will stand up, that is, not be altered or dissolvedwhereby the emulsion lying directly beneath such resist is protected andpreserved until it is desired to remove the resist. The resist isremoved with a nonaqueous solvent such as a solution of varsol,gasoline, turpentine or the like, in the manner indicated inconnectionwith the preparation of the negative. After removal of theresist, the film is placed in a developer, such as Eastman KodalithDeveloper, to develop the previously protected portions of the film andafterwards the film is washed and dried in the usual manner to producethe desired positive.

A further object of the invention is to provide either a wrong readingnegative or positive as the film is viewed from the emulsion side.Whether the film produced is a negative or a positive is determinedbythe particular sequence in which the particular film treating stepsare used as pointed out hereinbefore.

A further object of the invention is to provide a particular type resistwhich is particularly adapted'for use in the process of the presentinvention, said resist preferably comprising as a pigment one of thefluorescein dyes which dyes are well known in the art relating toprinting inks. It has been found that the resist which isbest adapted tothe present process consists of a Rhodamine B toner resist which isapproximately 30% pigment by weight.

A further object of the invention is to provide methods of producinglithographic film negatives and/ or positives from hot type. Whether ornot the negatives and/or positives thus produced are wrong reading orright reading when viewed from the emulsion'surf'ace can be determined,first, as towhether or not the emulsion surface of the film wasimpressed by dry offset from the blanket of a proof press, or secondly,whether or not the emulsified surface was'irnpressed directly from thetype of a proof press, and further the fact that the thus impressedfilms can be made positive or negative" as determined by selection ofthe particular sequence of steps to which the films are subjected. A

A further object of the invention is to provide methods of producingeither multiple wrong reading" negatives from a right reading positive,or multiple wrong reading positives from a right reading negative.

A further object of the invention comprises the production oflithographic film positives or negatives from a well known type proofpress in which the emulsion surface of the film is impressed with animage from the blanket of such a machine, the film having been deliveredto the grippers emulsion side down or impressed from the type of such apress. In the latter instance, the film is delivered to the grippersemulsion side up to take the impression directly from the type.

Now, describing the process more particularly with re spect to thefeatures of novelty therein, printing type of any construction is set upin the bed of any proof press designed to print simultaneously bothsides of a sheet of paper, acetate, etc. such as a Vandercook 4T. Itwill be understood that such type, when so set, is known in the art aswrong reading. The surface of the type form is then inked up in thenormal manner with the novel resist which the present inventiondiscloses, such resist, by way of example, consisting of 30% RhodamineB, 30% No. 1 varnish and 30% blanc fixe" (extender) plus about of otherextender (inorganic salts or other materials used to make inkcommercially practical) such resist being a quick setting, non-drying,high tact resist. The type of resist we have found to be best suitablefor our process and by way of example consists by weight of 11% partslithographic linseed varnish #1 (regular); 13 parts blanc fixe(precipitated barium sulphate); 2 parts precipitated calcium carbonate;10% parts Rhodamine B, pigment toner and a very small amount of achemical anti-skinning" agent. Next, in the process, an impression istransferred on the usual blanket, which impression is right reading.That is, the impression onto the blanket is an image of the type whichwas set up in the proof press, which type was set up wrong reading andthus when the impression was transferred to the blanket the same wasright reading in that the impression was reversed end for end, or as amirror image so to speak. Of course, it would be possible to set thetype in the press in right reading form and the impression thus producedfrom such would be wrong reading, wherein, if desired, the impression onthe emulsion surface of the film would be right reading. After theblanket has been thus impressed with the type, the image on the blanketis then transferred to the emulsion side of the film, which impression,as viewed from the emulsion side of the film, will be wrong reading. Thesame could be impressed in right reading form if so desired by usingright reading type as explained above.

The next step in the process is to expose the impressed film to normalroom light (or stronger) if the same has not already been so exposed tothereby fully and completely expose the same. Thereafter, the film isdeposited in a tray of film developer such as Eastman Kodalith Developeror to any developer recommended by the manu facturer of the particularfilm being used, and we have found that excellent results have beenobtained by a developer consisting of the following formula, by way ofexample:

Water, about 90 F 64 oz. (Avd. or U. S. Liq.)

This developer develops to a dense black color all portions of theemulsion surface of the film other than those portions covered by theresist image. The importance here is the fact that the resist is socomposed as to resist attack by the developer and consequently thatportion .4 of the emulsion covered by the resist is not developed.

The next step in the process is to wash off from the surface of the filmas much of the developer solution as possible by immersing the film fora short time in tap water. Thereafter, the film which now carries theresist only on those portions of the film Whereon the image wasimpressed is immersed in a bath of a non-aqueous resist-dissolvingsolution, such as a solution of varsol, gasoline, turpentine or thelike, and at the same time swabbing the film gently with a cotton wad orthe like to facilitate removal of the resist.

The next step in the treatment of the film comprises placing the film ina so-called hypo bath. For this purpose, there may be employed a fixingbath such as a solution of sodium thiosulphate consisting of thefollowmg:

Water, about 125 F oz Sodium thiosulfate lbs 3 Ammonium chloride oz 6%Sodium sulfite, dessicated oz 2 Acetic acid (28%) fiuid oz 6 Boric acidcrystals oz 1 Potassium alum oz 2 Cold water to make gallon 1 Action ofthe hypo bath on the film will remove the emulsion in those portionswhich were protected by the resist and which were consequently notdeveloped, dissolved or attacked by the developer. In this manner, thereis produced a clear, sharp negative which is wrong reading when viewedfrom the emulsion side of the film. Thereafter, the film is washed inwater for a few minutes to remove the excess hypo and is hung to dry.

In the event a positive print is desired, as where the same is to beused in a deep etch plate-making procedure, it is only necessary tofirst apply to the emulsion surface of the film the resist image desiredand then to treat the film with the aforementioned sodium thiosulphatesolution (hypo). The hypo solution in this procedure removes all of thesalts of the emulsion carried on the film except those portionsprotected by the resist, which of course would be the matter transferredfrom the impression blanket, it being understood that the resist is socomposed as to be insoluble in and unaffected by the hypo. Suchtreatment makes the film entirely transparent except for the portionsprotected and covered by the resist. After the hypo treatment has beencompleted, the film is washed in water, and is then deposited in a trayof a non-aqueous dissolving solution such as a solution of varsol,gasoline, turpentine or the like, which solution will dissolve theresist from the emulsion which has been protected thereby. The film isthen Washed in water and thereafter placed in a developing bath of thetype described hereinbefore. As a result of this step, that portion ofthe emulsion which was directly beneath the resist will show black on atranslucent background and thereby produce a positive film having awrong reading impression thereon when viewed from the emulsion side ofthe film. It will therefore readily be seen that in the production ofsuch a positive film that no camera is needed, and no photographicnegative need be produced to make such a positive therefrom as is theusual practice. The wrong reading positive thus produced is particularlysuitable for use in making deep etch lithographic printing plates.

As heretofore stated, if it is found to be desirable to produce anegative or positive lithographic film from a film which has had itsemulsion surface impressed directly from a type, it is possible to doso. During the process of producing such films, it should be understoodthat a proof press of any well known type may be used and the type maybe set up in the bed of the press and then covered with the particularresist of the present invention by the usual inking rollers. Thereafter,the usual tympan or blanket cylinder is passed over the type to. impressthe film and, in this feature of the invention,- the lithographic filmis inserted in the grippers on the t-ympan or blanket cylinder with theemulsion side of the film facing away from thetympan or blanket so thatwhen the tympan or blanket cylinder is moved across the type bed, theresist image is impressed to the emulsion surface of the film directlyfrom the type. The film impressed in this manner is right readingbecause it has taken an impression from the wrong reading type. Whenthis film. is treated in either of the sequence of steps set forthabove, we. obtain either a negative or positive, both right reading,depending upon the. sequence selected. Whether the film is negative orpositive. is determined by whether the film is treated first with thedeveloper, next with the solvent, and next with the hypo to produce aright reading negative or by treating the film in the sequence of firstwith the hypo, next with the solvent and finally with the developer tothereby produce a right reading positive. It will be understood that thefilm may be washed with ordinary tap water between the various steps ofthe process. It can not readily be seen that if the right readingnegative thus produced is placed with its emulsion surface adjacent orin contact with the emulsion surface of an unimpressed and unexposedfilm and light is passed through the negative film to the unimpressedfilm, a wrong reading positive will be produced. Conversely, if theimpressed surface'emulsion side of the positive right reading film ispositioned in contact with or adjacent the emulsion surface of anunimpressed and unexposed film, and light is passed through from theside of the positive, a wrong reading negative will be produced.Therefore, such right reading negatives or positives are used when it isdesired to make multiples or duplicates of like subject matter. Thewrong reading negatives produced from the positive film may be used formaking albumin process plates while the wrong reading positives can beused in deep-etch work. It should be understood that the application ofthe resist to the emulsion surface of the film can be done by handrather than from type or by a machine and the type can be set by hand orotherwise and therefore no proof press is essential in carrying out theprocess insofar as the present method of producing right readingnegatives and positives is concerned.

In order to produce a white opaque positive, it is only necessary toperform first the step of placing the film in a hypo which will removeall of the salts of the emulsion other than that protected by theresist, then, dissolve the resist by placing the film in a bath of adissolving solution such as varsol, gasoline, or the like, and afterusing the developing bath a bleaching bath containing some well knownsilver bleaching chemical such as sodium hypochlorite can be used. Thebleaching bath bleeches the developed portions of the impressed imageand such portions are rendered partially opaque.

It will therefore be understood that in the process outlined above, thatthere have been disclosed a number of processes of producing and makingeither positive or negative films for use with lithographic printing,first of all by providing methods in which either a photolith negalivefor producing albumen plates or a photolith positive for producingdeepetch plates may be prepared in both of which the reading is wrongreading when viewed from the emulsion side. Inasmuch as lithographicplates are normally right reading, it is highly desirable that theimpressed fihn be wrong reading when viewed from the emulsion side sothat the emulsion side of the film can be placed directly in contactwith the sensitized surface of the lithographic plate and thereby avoidany spread or undercutting of the light when using the present film forproducing the printing plates.

Dark room conditions are not necessary and as a matter of fact theentire sheet of film must be preexposed before the processes can beperformed.

With the processes above disclosed corrections are much simplified inthat all that is necessary is to correct the type and pull a newnegative which will eliminate the time consuming step of stripping-inappropriate corrections.

And again in the present method, the negative may be ruled with theresist by a scriber directly on the negative.

While the particular resist above disclosed has been found entirelysatisfactory for the present process, it is contemplated that many otherfluorescein pigments may be used in place of the Rhodamine B abovedisclosed to obtain a similar result.

What is claimed is:

1. A protective resist for use in the preparation of a film for makinglithographic plates comprising approximately 30% Rhodamine B pigment andapproximately 60% of a carrier therefor comprising approximately equalparts of varnish and blanc fixe and approximately 10% inorganic saltextenders.

2. The method of making from a uniformly preexposed silver halideemulsion coated lithographic film a negative from which printing platesmay be produced, comprising the steps of applying tothe face of type animage-producing resist of the composition set forth in claim 1,transferring the resist from the type face to a printing blanket,transferring the resist from the printing blanket to the emulsion sideof said uniformly preexposed film, completely exposing the film tolight, subjecting the exposed film to a first chemically active agentreactive with the emulsion surface of the film but not reactive withsaid resist, dissolving the resist, reacting the protected portion witha second agent to produce an image of said type face on said film, andfinally washing and drying the negative thus produced.

3. The process of making, for use in producing multiple positives, aright reading negative from a uniformly pre-exposed silver halideemulsion coated lithographic film comprising the steps of impressing aprotective resist of the composition set forth in claim 1 on selectedareas of the emulsion surface of the film, treating the film soimpressed with a silver halide developer to develop that portion of theemulsion not covered by the resist, applying a solvent to the resist toremove said resist from said surface, treating the film with athiosulfate solution to remove from the film the previously protectedportion of said emulsion, and washing the negative thus produced.

4. The process of making, for use in producing multiple negatives, aright reading positive from a uniformly pre-exposed silver halideemulsion coated lithographic film comprising the steps of impressing aprotective rcsist of the composition set forth in claim 1 on selectedareas of the emulsion surface of the film, treating the film soimpressed with a thiosulfate solution to remove from the film thatportion of the emulsion not covered by the resist, applying a solvent tosaid resist to remove said resist from said surface, treating the filmwith a silver halide developer to develop the previously protectedportion of said surface, and washing the positive thus produced.

5. The method of making a film for use in the production of lithographicplates comprising the steps of impressing on selected areas of theuniformly pre-exposcd silver halide emulsion surface of a lightsensitive photographic film a water-insoluble protective resist of thecomposition set forth in claim 1 which is non-reactive with silverhalide photographic developers and thiosulfate solutions, fully exposingthe film to light, treating the film with a first chemically reactivephotographic solution which is a silver halide developer for theunprotected areas of said emulsion surface, removing the resist with anon-aqueous solvent therefor which is non-reactive with said emulsionsurface, treating the previously pro tected areas with a secondchemically reactive photographic solution which is a thiosulfatesolution reactive with said previously protected areas to produce animage, and then Washing and drying the negative thus produced.

6. The method of making a film for use in the production of lithographicplates comprising the steps of applying to selected areas on the coatingof a film having a chemically reactive silver halide coating on one sidethereof, in the presence of light, a protective resist of thecomposition set forth in claim 1, subjecting the film to the action of asolution selected from the class consisting of silver halide developerand thiosulfate solution, removing said resist from said selected areasand subjecting the film to the action of the other member of said classto produce an image on said film corresponding to the selected areas towhich said protective resist is applied.

7. The method of making a film for use in the production of lithographicplates comprising the steps of impressing on selected areas of theuniformly pre-exposed silver halide emulsion surface of a lightsensitive photographic film a water-insoluble protective resist which isnon-reactive with silver halide photographic developers and thiosulfatesolution, said resist having the composition set forth in claim 1, fullyexposing the film to light, treating the film with a first chemicallyreactive photographic solution which is reactive with the unprotectedareas of said emulsion surface, removing the resist with a non-aqueoussolvent therefor which is non-reactive with said emulsion surface,treating the previously protected areas with a second chemicallyreactive photographic solution which is reactive with said previouslyprotected areas to produce an image, and then washing and drying thenegative thus produced.

8. The method of making a film for use in the production of lithographicprinting plates, comprising the steps of coating a type face with aresist of the composition set forth in claim 1, transferring said resistfrom said type face to the silver halide emulsion side of a uniformlypre-exposed light sensitive photographic film, completely exposing thefilm to light, treating the film with a first agent which reacts withthe portion of the emulsion not protected by the resist, washing andtreating the film with a solvent for said resist, treating the film witha second agent which reacts with the portion of the emulsion previouslyprotected by the image-resist to render the image permanent, and washingand drying the positive film thus produced.

References Cited in the file of this patent UNITED STATES PATENTS868,779 Hammer Oct. 22, 1907 1,700,262 Heinecke Jan. 29, 1929 1,892,875Dietz Jan. 3, 1933 1,901,799 Brooks et al Mar. 14, 1933 1,913,881Heinecke June 13, 1933 1,922,548 Mattin Aug. 15, 1933 2,152,856 SwitzerApr. 4, 1939 2,306,887 Klose Dec. 29, 1942 2,319,079 Murray et al. May11, 1943 2,503,790 Yule Apr. 11, 1950

1. A PROTECTIVE RESIST FOR USE IN THE PREPARATION OF A FILM FOR MAKINGLITHOGRAPHIC PLATES COMPRISING APPROXIMATELY 30% RHODAMINE B PIGMENT ANDAPPROXIMATELY 60% OF A CARRIER THEREFOR COMPRISING APPROXIMATELY EQUALPARTS OF VARNISH AND BLANC FIXE AND APPROXIMATELY 10% INORGANIC SALTEXTENDERS.